Characterizing the diversity of PmB aging with application to pavements

• Three PmBs aged via RTFOT+3PAV, VBA, and 6-/36-month field exposure. • Examined chemical, rheological, and morphological properties. • Polybutadiene indices can misrepresent polymer degradation. • Field aging oxidizes base bitumen while preserving SBS polymer. • Excess base bitumen oxidation negates residual SBS benefits. The aging behavior of Polymer modified Bitumen (PmB), widely used in road pavement applications, is significantly more complex than conventional bitumen. The polymer-bitumen interactions can cause multiple aging effects to occur simultaneously. To elucidate these processes, three PmBs were subjected to two laboratory long-term aging procedures and field exposure. Chemical, rheological, and morphological properties were evaluated using Fourier Transform Infrared (FTIR) Spectroscopy, Dynamic Shear Rheometer (DSR), and fluorescence microscopy. The study reveals that FTIR-derived polybutadiene (PB) indices alone are inadequate for reliably tracking polymer degradation due to overlapping chemical absorptions and morphological artifacts, emphasizing the need for complementary analytical techniques. Comparative analysis further shows that conventional laboratory aging induces greater polymer degradation compared to field exposure, where polymer networks remain better preserved even after 36 months. Additionally, polymers with higher vinyl content exhibited improved compatibility with bitumen and greater resistance to oxidative degradation. Overall, this study sheds light on PmB aging mechanisms and provides valuable guidance for designing more durable materials, refining aging simulations, and supporting future recycling strategies.